When the cardinals met in conclave, mainly by the intervention of Cardinal Granvelle, viceroy of Philip II. in Naples, Cardinal Buoncompagni was elected almost immediately, and proclaimed under the title of Gregory XIII. (1572-85). He had been a distinguished student and professor of law at the University of Bologna, where he had the honour of having as his pupils many of the ablest ecclesiastics of the age. Later on he was sent as confidential secretary to the Council of Trent. On his return from this assembly he was created cardinal, and appointed papal legate in Spain. At the time of his election to the Papacy he had reached his seventieth year. As a young man his life was not blameless from the point of view of morality, but after he became a priest nothing could be urged against his conduct even by his worst enemies. Though it must be admitted that he was not of such an ascetic and spiritual temperament as his predecessor, he was a man of irreproachable character, not over anxious to promote his own relatives, and determined to strengthen the Catholic Church by raising the standard of education and by appointing to the episcopate none but the most worthy ecclesiastics. Hence he drew lavishly upon the funds of the Holy See to erect Catholic Colleges in Rome and in several countries of Europe. He founded the magnificent /Collegium Romanum/for the education of students from all parts of the world, and placed it under the administration of the Jesuits, in whom he reposed the most signal confidence. As the circumstances that led to the establishment of the /Collegium Germanicum/ had not improved, he conferred on it more generous endowments, and united it later on with the college which he had founded for the Hungarians. Owing to the persecutions in England and Ireland and the suppression of institutions for the education of the clergy, Gregory XIII. founded an English College (1579) and provided funds for the erection of an Irish College. The money intended for this latter institution was spent in assisting the Irish in their wars against Elizabeth. In addition to this, more than twenty colleges situated in various parts of Europe, amongst them being the Scotch College at Pont-a-Mousson, owe their origin in whole or in part to his munificence. He was, also, very determined that none but the most worthy men should be appointed to episcopal sees, and with this object in view he took pains to inquire personally about the merits of distinguished ecclesiastics in each country, and to prepare lists of them for use as vacancies might arise. He was equally careful in the appointments which he made to the college of cardinals. In order to keep touch with the progress of affairs in Germany he established a nunciature at Vienna in 1581, and another at Cologne in the following year. The results of this experiment were so successful that in a short time nunciatures were established in nearly all the Catholic countries.[3]
Like his predecessor he was determined to continue the war against the Turks, but the circumstances were unfavourable in France and in the Empire, while Venice and Spain, the former allies of the Holy See, concluded peace with the Sultan. In England and Ireland neither by peaceful measures nor by the expeditions fitted out by him in connexion with the Desmond Rebellion was he able to achieve any lasting results. His legates succeeded in inducing John III. of Sweden to abjure heresy and to return to the bosom of the Catholic Church, but, unfortunately, the conversion lasted only until political circumstances demanded another change. In Russia his representatives arranged a peace with Poland, and put an end for the time to any active persecution of Catholicism within the Russian dominions.[4] In all parts of Europe, where Catholic rulers found themselves in difficulties, subsidies were sent by Gregory XIII. to their assistance. Charles IX. in France, Philip II. of Spain, Austria, the Knights of Malta, and the Catholics of England and Ireland shared largely in his munificence.
He issued a new edition of the Roman Martyrology in 1584, and directed that it should be used to the exclusion of all others. His predecessor had appointed a committee of jurists to prepare a revised edition of the Decrees of Gratian. He had been a member of that commission, and as Pope he brought the work to a successful conclusion. But the achievement for which he will be best remembered is undoubtedly the Gregorian Calendar. The errors of the calendar had been noticed by many, but how to correct them and prevent them for the future was the problem that was still unsolved. Gregory XIII. appointed a body of experts to examine the subject, the most prominent of whom were the Jesuit Father Clavius and Cardinal Sirleto. The committee had the advantage of having before them the papers of the Italian scientist, Lilius, and the suggestions of the Catholic universities. In 1582 the Gregorian Calendar was published, and was accepted generally in all the Catholic countries of Europe. But for a long time the Protestant countries, believing that nothing good could come from Rome, remained attached to the old style. It was only in 1700 that the Gregorian Calendar was accepted in Germany and Holland, and at a still later period (1752) England consented to the change. The following year Sweden followed suit, and by 1775 the use of the new calendar had become general outside Russia and the other countries involved in the Eastern schism, in which the old style is followed till the present day.